Spectrometer Solenoid Design and Test Results

1. Spectrometer Solenoid Design and Test Results Steve Virostek Lawrence Berkeley National Lab Spectrometer Solenoid Review November 18, 2009

2. MICE Cooling Channel Layout Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

3. Topics • Magnet 1 design features • Magnet 1 testing results • Modifications for Magnet 2 • Magnet 2 test results • Photos for discussion Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

4. Magnet 1 Original Design Cold head 2nd stage Cold head 1st stage Vapor return lines LHe lines Cold mass Radiation shield Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

5. Temperature Sensor Locations TPR: platinum resistor TRX: Cernox HTR: heater TSD: silicon diode VTM: voltage tap Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

6. Magnet 1 Testing Results • Magnet cold mass was successfully cooled down to <5K using a combination of LN and LHe • Cool down of the shield was very slow as there was no direct connection to the LN (i.e. shield cooling by radiation and conduction thru cold mass suppts only) • LHe was boiling off from cold mass at a high rate • Helium was not being condensed at all by the coolers • Since the magnet was cold, an attempt was made to train the coils Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

7. Magnet 1 Testing Results (cont’d) • The training reached 196 A in all coils (270 A needed to reach 4 T in the central coil) • Magnet training was discontinued when the available cryogens ran out and so modifications could begin • Based on measurements and observations, the coolers were not maintaining the LHe level, and the shield temperature was ~120 K rather than the specified 80 K • These two issues were due to the thermal siphon line being plugged by frozen N2 and an inadequate thermal connection between the cooler 1st stages and the shield Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

8. Magnet 1 Testing Results (cont’d) • The blocked helium lines was mainly a procedural and partially a design issue • Also, the pressure rise observed within the cold mass during quench was too high • It was determined that the venting of the cold mass during quench was not sufficient due to crowding of the single vent line with instrumentation wires • Several mechanical issues also arose: magnet alignment in vacuum vessel, support stand height, iron shield support pads, support stand offset Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

9. Magnet Design Modifications • Based on the results of the Magnet 1 testing, several design modifications were proposed • Work proceeded to complete the Magnet 2 assembly with design changes while starting Magnet 1 disassembly • A new cold mass cooling scheme was devised as well as an improved cooldown procedure • The 1st stage radiation shield connection was modified an an attempt to increase the thermal conduction • An additional vent line was added to the cold mass • An LN reservoir was added for direct cooldown of shield Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

10. Magnet Cooling Configurations Cold head Condenser Larger diameter Cold mass shell Direct connection LHe line Coils No trap LHe Trap Original Design Design Option A Design Option B (not adopted) (Magnet 1) (Magnet 2) Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

11. Cryostat and Cooling System Mods Cold head 1st stage Direct cryostat connection option 1100 Al radiation shield connections Additional vent line Radiation shield Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

12. Modified Recondensing System Liquid/vapor He accumulator and cryocooler sleeves Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

13. Liquid Nitrogen Reservoir • Reservoir provides direct LN cooldown of shield • May improve thermal connection between 1st stage of cryos and shield • Frozen mass of nitrogen protects leads in event of power failure (if LN is left in reservoir and temp. is low enough) Vent/fill lines (3) 1st stage cooler connection LN reservoir Thermal plate connection Radiation shield Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

14. Magnet 2 Testing Results • After completing the described modifications earlier this year, an attempt was made to cool Magnet 2 with cryogens • An ice blockage developed within the cold mass fill line • The fill line geometry (90° bends) prevented clearing of the blockage, and the vendor moved the stinger to a vent line • Continuing the fill process led to a leak in a Conflat flange in the 2nd vent line (the one not being used for filling), venting the vacuum space to helium and aborting the cooldown • The Magnet 1 fill line routing has been changed to avoid sharp bends and thus improve the ability to clear a blockage Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

15. Magnet 2 Testing Results (cont’d) • After warming up the magnet, the Conflat flanges were replaced with welded joints • Since the fill line blockage was likely a procedural issue, a safer and more robust technique for cooldown was devised (Bross/FNAL) and has worked well • The subsequent cooldown was successfully completed in only ~3 days w/o incident • However, the shield temperature fell slowly to only about ~115 K at the ends of the cylinder, resulting in added heat flow into the cold mass via the cold mass supports Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

16. Magnet 2 Measured Temperatures 80K (no current) 90-95K (182 to 238 A) Not working 74K 65K 102K min No other shield sensors here Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

17. Magnet 2 Testing Results (cont’d) • The improved(?) shield thermal connections and the LN reservoir did not solve the previous shield problems • The coolers are expected to maintain the LHe level after filling; ~1% of the LHe was being lost overnight (unpowered) • At this point, training began and appeared to be going well • The magnet underwent five training quenches at currents ranging from 182 to 238 A • At 238 A (w/all coils in series), one of the HTS leads burned out due to a higher than allowable temp. at the upper end Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

18. Magnet 2 Testing Results (cont’d) • The upper lead temperature without current was ~80 K, increasing to >90 K with current, eventually resulting in failure of the lead farthest from the coolers • The lead problem was a surprise, as it was not noticed in the earlier Magnet 1 tests; the feedthroughs and all the leads are the same ones used before in Magnet 1 • We are currently thermally testing the feedthroughs and leads in an off line test to see what can be learned Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

19. Testing Results Discussion • Changing flexible connection does not appear to have had a major impact on shield temperatures • New Al straps are thicker than the original Cu, but the Cu conductivity was better and the original straps were shorter • Our vendor, Bert Wang, has stated that he believes the connection to the shield is inadequate • There have been no indications of vacuum problems other than the seal failure that occurred in the vent line • No local icing has been observed on the vacuum vessel • Temperature measurements using a thermal laser probe have not revealed any irregularities Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

20. Photos for Discussion Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

21. Upper Leads and HTS Leads Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

22. Upper Leads and Thermal Intercepts Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

23. Upper Leads and 300K Feedthrough Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

24. Upper HTS Leads Thermal Intercept Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

25. SC leads at cold mass feedthrus Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

26. Coil Taps & Intercepts for Lower HTS Leads Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

27. Coil Taps & Intercepts for Lower HTS Leads Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

28. Magnet 2 HTS Leads (right lead burned out) Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

29. Radiation Shield Thermal Connection 6061 Al cylinder ~6 mm thick Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

30. Upper Thermal Shield Connection 1st stage Cu plate Cu/Al transitions (10 each) 6061 Al cylinder ~6 mm thick Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

31. Magnet 1 Shield Flexible Connection OFHC copper straps Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

32. Magnet 2 Shield Thermal Connection 1100 series aluminum connection to thermal shield (previously thin copper) Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

33. Magnet 2 Shield with Flexible Connections Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

34. Plates Welded to Shield for LN Reservoir Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

35. MLI Wrapped Cold Mass and Shield Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

36. Partially Assembled Magnet Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

37. Close Up of Cold Mass End Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

38. MLI on Shield & Vacuum Vessel Inner Bores Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

39. MLI Wrapped Cooler Sleeves and Leads Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

40. Cold Mass Connections (Magnet 1) Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

41. Cold Mass Support during Fit Up Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

42. Cold Mass Support Connection to Shield Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

43. Thermal Shield Support Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

44. Temperature Sensor on Cold Mass Bore Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009

45. LHeCooldown of Magnet Steve Virostek -- Lawrence Berkeley National Laboratory -- November 18, 2009